The present invention, in general, is directed to inset luminaires adapted to provide a substantially uniform distribution of light along a low vertical angle. The present invention, more particularly, is directed to flush luminaires capable of being mounted in pavement, and configured to provide a generally low angle of visibility of substantially uniform light, in such applications as airfield runway and taxi-way lights as well as pedestrian crosswalk lights and the like.
Inset and recessed lights are known in the art for use in a variety of applications, spanning from high-end technical applications, such as runway centerline airport lights, to specialized design or architectural and other decorative lighting applications. There are, in general, two categories of such lights. One category, flush, has no elevation above the surface. Another category, semiflush, has only minimal elevation above the surface.
A conventional luminaire consists of a housing that is recessed or flush relative to the surface, a light source, and an optical element which directs light in a desired manner. In many such luminaires, a commercially available tungsten-halogen or similar lamp with a reflector is often used as a light source. Such a lamp is able to provide light distribution which may be characterized by a high concentration of luminous flux along the optical axis and in relatively small solid angles, e.g. 10xc2x0 to 200xc2x0, relative to the optical axis, i.e., the so-called xe2x80x9cmain beamxe2x80x9d of the conventional lamp. The optical element, in general, is frequently used to redirect the luminous flux generated by the lamp. There are presently two principal designs of optical elements in use. One such design (e.g., U.S. Pat. No. 5,669,691) uses a prism whenever it is desirable to direct light along a somewhat restricted horizontal angle, usually not exceeding 30xc2x0 to 40xc2x0, above a reference surface. Still another conventional design (U.S. Pat. No. 5,556,189) uses a combination of lenses, e.g., cylindrical and spherical, whenever it is desirable to provide a substantially omnidirectional light distribution, in a horizontal plane above the surface.
One disadvantage of such conventional construction is that most of the generated light is not able to be directed in low horizontal angles, for the reason that neither design is configured to change the light distribution. Another disadvantage relates to physical limitations of shape and dimensions of lenses, making flush omnidirectional luminaries impractical, especially whenever a low vertical angle light distribution pattern is desired. A further disadvantage of such conventional construction is low efficiency, as much of the luminous flux generated by the light source becomes lost or vignetted (i.e., shaded) by the luminaire components and is not emitted outward in the light pattern desired.
One object of the present invention is to provide a flush luminaire having a predetermined distribution of light in the horizontal plane.
Another object of the present invention is to provide a flush luminaire having an omnidirectional distribution of light in the horizontal plane.
Yet another object is to provide a flush luminaire having a high intensity output, especially in low vertical angles.
Yet another object is to provide a flush luminaire with higher efficiency than is currently available.
A further object is to provide such a luminaire of universal design, and which is suitable for such applications as architectural and decorative lights, airport and heliport lights, traffic and pedestrian lights, and the like.
Still another object is to provide such a luminaire, simpler to install and less expensive to manufacture than presently available.
To accomplish the above objects as well as other objects, features and advantages of the invention, the flush luminaire is configured to provide a predetermined (directional or omnidirectional) distribution of light about a substantially horizontal surface. The term xe2x80x9comnidirectionalxe2x80x9d as used throughout this patent specification shall be understood to mean xe2x80x9cbeing in or involving all directions in the horizontal plane,xe2x80x9d in contrast to the term xe2x80x9cdirectional,xe2x80x9d which shall be understood to mean xe2x80x9cbeing in or involving a limited angle in the horizontal plane.xe2x80x9d
The flush luminaire of the present invention comprises a housing, an optical window, a light source, and an optical element. The housing has an internal cavity disposed beneath the horizontal surface and defines an opening disposed adjacent the horizontal surface. The optical window, preferably transparent and substantially flat, has a surface that overlays the housing opening. The light source, which is disposed within the housing cavity, provides a spatial light distribution pattern which defines an optical axis that is disposed substantially perpendicular relative to the optical window surface. The optical element, also disposed within the housing cavity, redistributes light rays emitted by the light source along preselected angles relative to the horizontal surface, directionally or omnidirectionally.
Further in this regard, one embodiment of the invention directs light beams omnidirectionally about a vertical axis disposed perpendicular relative to the horizontal surface, wherein the light beams are disposed above the horizontal surface. In another embodiment, the light beams are disposed substantially parallel to the horizontal surface.
In reference to the flush embodiment of the present invention, the flat transparent optical window is preferably disposed substantially parallel to the horizontal surface. In that regard, one particularly preferred embodiment of the light source is a light-emitting diode; and a preferred embodiment of the optical element is a prismatic structure.
In general, light-emitting diodes (LEDs) are known to generate heat; and LED longevity is thus dependent upon the removal of such LED-generated heat. As a result, the flush luminaire of the invention further preferably includes an effective amount of heat-transfer surface, so disposed adjacent the light-emitting diode (LED) as to be in a heat-transfer relationship with the LED, to provide removal of any such LED-generated heat, for providing desired longevity of the LED or other heat-generating light source.
Further in that regard, LED performance is known to be temperature dependent, principally because of semiconductor components associated with the light-emitting diode. Accordingly, the LED-generated heat is effectively removed, and the resulting ambient temperature effectively controlled, by a conventional temperature-control device that is configured and so dimensioned as to be disposed preferably within the housing cavity adjacent the light source and in association with the heat-transfer surface, which results in a substantially uniform preselected temperature profile being achieved for the light-emitting diode as well as for any other heat-generating light source that is selected.
In another preferred embodiment of the present invention, the optical element comprises a prismatic light transformer (PLT) which is disposed between the light source and the optical window and that is configured to provide optimal light output relative to the horizontal surface in response to light from the light-emitting diode. In still another preferred embodiment of the invention, the optical element comprises prismatic structure that is integrally formed on the optical window surface.
Still in another preferred embodiment of the present invention is a prismatic light transformer designed as a circular prismatic light transformer (CPLT), which is configured to provide omnidirectional light output relative to horizontal surface.
In yet another embodiment of the flush luminaire of the present invention, the light source comprises a plurality of light sources each of which produces a single light beam, and the plural light beams are integrated such that every light beam is offset from the horizontal surface by substantially the same angle relative to every other light beam.
In a further embodiment of the flush luminaire of the present invention, the spatial light distribution pattern has a substantially circular maximum that is substantially centered on the optical axis. In yet another embodiment of the luminaire of the invention, the spatial light distribution pattern presents a substantially circular maximum light intensity envelope that is offset from the optical axis. In a farther embodiment of the present invention, the flush luminaire includes an especially designed mechanism for providing controlled distribution of light relative to the vertical axis.
The flush luminaire of the present invention further comprises a power supply disposed within the housing cavity. In one embodiment of the present invention, the power supply comprises batteries. In another embodiment of the invention, the power supply is operably connected to an external power source. External power sources that are suitable for purposes of the present invention include, in general, commercial power lines and, in particular, a generator (e.g., diesel or gasoline powered), for the purpose of providing power during emergency situations when commercial power is interrupted or otherwise not available.
These and other features and advantages of the invention will be apparent to those skilled in the art, after referring to the following description and accompanying drawings.